Are we making mouse brains bigger?

Maybe urban living makes all of us smarter:

In two species — the white-footed mouse and the meadow vole — the brains of animals from cities or suburbs were about 6 percent bigger than the brains of animals collected from farms or other rural areas. Dr. Snell-Rood concludes that when these species moved to cities and towns, their brains became significantly bigger.

Dr. Snell-Rood and Ms. Wick also found that in rural parts of Minnesota, two species of shrews and two species of bats experienced an increase in brain size as well.

Dr. Snell-Rood proposes that the brains of all six species have gotten bigger because humans have radically changed Minnesota. Where there were once pristine forests and prairies, there are now cities and farms. In this disrupted environment, animals that were better at learning new things were more likely to survive and have offspring.

Studies by other scientists have linked better learning in animals with bigger brains. In January, for example, researchers at Uppsala University in Sweden described an experiment in which they bred guppies for larger brain sizes. The big-brained fish scored better on learning tests than their small-brained cousins.

There is more here, via Michelle Dawson.


Domestication tends to decrease brain size.

On the other hand, suburbanization does seem to favor clever jack-of-all-trade predators, such as crows, coyotes, and black bears.

How does one devise a learning test for guppies?

Mazes slotted into the tanks, then measuring how long the guppy takes to solve them for a food reward.

You can also use shuttle boxes for fish. That's where they have to jump over a barrier when the light comes on to avoid an electric shock.

Human brain size has been decreasing since people started living in cities.

Don't make the Skinner Box in the streets of Manhattan. That would be unfair.

"Brain: the large piece of wax between the ears." (a provincial lexicographical entry)

It's all fun and games until we are conquered by a race of big-brained super rats.

I for one welcome our new Vole overlords.

James Herbert, alas recently deceased, was a Brit. sci fi writer who wrote a "giant rat invasion" trilogy...

Does the Flynn effect have an urban vs rural dimension? How do their IQs differ, once one controls for the selection bias of smart rural people moving to the city?

Could also be nutrition. Eating garbage gives you easy calories compared to hunting, reducing the fitness penalty for having big calorie-hungry brains.

but also reducing incentives for cleverness in finding food -- and possibly also for avoiding predators, neh? since more (available) food might allow less risk-taking for equal-or-better food-rewards?
Hence leading to stupider, not smarter ...???
Bigger brains notwithstanding, perhaps ...
More convincing-&-relevant would be direct IQ testing of rural-vs-urban mice ...

Having not read the paper, I can't properly criticize the findings. However, I wonder how they controlled for food availability and selection. Rural rodents are limited to seasonal variations and other factors that urban ones do not encounter. It could be that the urban animals do not experience caloric restrictions (less food in winter) and have access to a wider variety, and as a result are simply better fed. The black bears in Yosemite are forgoing hibernation because of the year round availability of food, which may be the same factor in play. Finally, brain size has not proven to be a factor in intelligence. Corvids have much smaller brains than many mammals but demonstrate far greater aspects they we consider to be hallmarks of intelligence. The only thing this study appears to show is the overall ignorance of humanity, which is not all that novel or impactful. We are a nation of morons aspiring to be imbeciles, we look to idiots for guidance and exalt fools as demi-gods.

Bird brains are fundamentally different from mammal brains in multiple ways from neuron size to organization, however most birds have relatively large brains compared to boddy size and corvids are exceptional in this department. Remember weight is something that has been relentlessly and aggressively selected against among birds for more than 100my.

How come city-dwelling squirrels are apparently no better at dodging cars than their country cousins?

I wonder if they looked at the availability of cooked, therefore more easily digested, food sources?

Yes, they make them human sized now.

Rat brain - that was the insult the Psychlos kept shouting at humans in Battlefield Earth.

I wonder why they didn't directly report brain size as % of mass? That correlates much better with 'intelligence' metrics. I suspect this is because they wouldn't have found an interaction...they control for size by body length, tail length, and foot length as a proxy for body size...

I don't buy it.


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